The present invention relates to systems and methods for improving vascular blood flow, and more specifically (A) for improving arterial blood flow in the lower extremities by (a) increasing venous blood flow and (b) enhancing functionality of the vessels with high shear rates through compression of specific portions of the foot, ankle, and calf of a patient, and (B) for reducing the incidence of venous blood clot formation in the lower limbs by creating pulsatile venous flow and promoting venous emptying.
Improvement of arterial blood flow in patients with obstructions of the arteries to the leg is usually obtained by surgically bypassing the occluded arteries, or by removing obstructions with devices that are inserted into the blood vessel. In elderly patients who have undergone multiple vascular procedures, the deterioration of arterial blood flow can lead to severe pain (ischemic neuritis), tissue loss (arterial ulcers), or toe loss (gangrene). When the arteries cannot be repaired anymore, this situation may lead to leg amputation.
In order to increase vascular blood flow without surgery, devices are sometimes used which apply a compressive force to various designated areas of the foot or leg. This compressive force is designed to increase the amount of blood returning to the heart through the veins, thereby increasing the arterial blood flow to the extremity. These compressive forces are typically designed to mimic a walking action which helps to push blood through the veins to the heart.
In normal walking, the foot is intermittently weight bearing, a result of which is to flatten the plantar arch. This flattening motion causes a spreading force between the ball and heel of the foot and a squeezing of the sole of the foot. This action produces a foot-pump action that helps to increase the venous blood flow in the leg. Prior art devices have therefore focused on mimicking such a flattening of the plantar arch. This is usually performed by wrapping a bladder completely around the foot between the heel and the ball of the foot. A fluid is then injected into the bladder in order to create a compressive force both on the top and bottom of the foot. Such an approach, however, creates several problems.
Devices that compress the feet of certain sensitive patient groups, such as diabetics, may irritate the skin and ultimately lead to skin breakdown over the bony areas at the midtarsal region. The compression of this midtarsal region thus leads to a situation where compression therapy for a particular class of patients must be limited in duration in order to avoid such tissue breakdown. It would, therefore, be advantageous to allow compression therapy of this class of patients over a longer period of time without breakdown of the skin over the bony areas at the midtarsal region.
In addition to the breakdown of tissue over the midtarsal region for certain groups of patients, prior art devices also are not usable on that portion of the patient population which have abnormally shaped feet. For certain patients, a bladder which completely encircles the foot and extends in a region from about the heel to the ball of the foot will not fit. It would, therefore, be advantageous to allow compression therapy on a wide range of patients including those having abnormal foot shapes.
For certain patients who have extremely sensitive feet, the application of a compressive force on both the top and bottom of the foot can cause tremendous pain. Patients who have had reduced blood flow in the lower extremities for a long period of time are especially susceptible to pain when compression therapy of the foot is initiated. It would, therefore, be advantageous to allow for a treatment regime which gradually increases a patient""s tolerance until compression therapy of the foot can be tolerated.
Finally, because the bladder completely encircles the foot, it can be difficult to assess the effectiveness of the treatment or to identify any developing problems. Since the bladder covers almost the entire foot, visual inspection can be difficult. Often to assess the effectiveness and identify developing problems, the treatment must be stopped and the device removed. It would, therefore, represent an advancement in the art to allow increased visual inspection during treatment with little or no impact on the effectiveness of the treatment.
Another problem suffered by patients is deep vein thrombosis. Deep vein thrombosis (DVT) is the formation of thrombus in the deep veins of the lower limb. DVT may follow trauma or surgery and is often associated with activated blood clotting factors and/or very slow blood flow called stasis. External pneumatic compression prevents stasis by two possible mechanism types: (1) a small volume of blood is accelerated to a relatively high velocity for a short period of time, and a large volume of blood is accelerated to a relatively low velocity for a longer period of time. Foot compression devices such as that described by Cook in U.S. Pat. No. 5,354,260 are examples of the first type in that the relatively small foot blood volume is accelerated rapidly to a high velocity. Calf and thigh compression devices such as that described by Hasty in U.S. Pat. No. 4,013,069 are examples of the second type in that a large blood volume in the calf and thigh are accelerated to relatively lower velocities for periods of time that typically exceed that of foot only compression types.
Since foot only compression does not significantly effect flow in some of the large veins in the calf (such as the so-called soleal sinuses where thrombi often originate), calf vein thrombi are still a large potential problem. Calf and thigh compression may move larger amounts of blood but stasis is better reduced with high blood velocities. It would, therefore, be desirable to be able to both create high blood velocities and move large blood volumes to provide patients with prophylaxis against deep vein thrombosis.
The foregoing problems in the prior state of the art have been successfully overcome by the present invention, which is directed to a system and method for increasing vascular blood flow in the lower extremities. Embodiments within the scope of the present invention may include a foot compression portion and a calf compression portion. The foot compression portion is designed to place compressive forces on particular locations of the foot and ankle. For example, embodiments may apply an upward compressive force to the sole of the foot from in front of the heel and extending past the ball of the foot to the phalanges. By extending the compressive force past the ball of the foot to the phalanges, the present invention more closely mimics the bend of the phalanges that occurs during waking.
Embodiments may also apply a downward compressive force in front of the tarsal region and a downward compressive force in the upper tarsal region. In these embodiments, the present invention leaves the midtarsal region open. This design carries several advantages over the prior art. For example, leaving the midtarsal region open allows visual inspection of the skin over the midtarsal region. This allows assessment of the health of the skin tissue by looking at the color and texture of the skin. Skin blood flow can also be assessed by applying sensors such as a laser Doppler flux probe or a photo plethysmographic probe. Finally, an underlying artery can be palpated for pulsatility by hand or by using an electric monitor incorporating a strain sensitive element or continuous wave ultrasonic Doppler probe that is placed on the skin over the artery.
Another advantage of leaving the midtarsal region open is that skin breakdown for sensitive patient groups, such as diabetics, is dramatically reduced thereby allowing for longer term application of compressive therapy. Finally, by placing straps to exert compressive forces only below the tarsal region and in the upper tarsal region, patients with a wide variety of foot shapes, including abnormal foot, shapes, can be more readily accommodated. Preferably, at least a portion of the dorsalis pedis artery in the region from where the deep plantar artery separates from the dorsalis pedis artery to where a portion of the dorsalis pedis artery descends between the proximal phalanges is open to allow visual and/or instrumental monitoring of blood flow.
Embodiments of the present invention may also apply a compressive force around the Achilles tendon anywhere in a region bounded essentially by the posterior portion of the calcaneus, the medial malleolus of the tibia, the Achilles tendon, and the posterior portion of the navicular. Applying compressive forces in this region actuates a pump that helps to push blood through the veins toward the heart.
The calf compression portion of the present invention is designed to apply a compressive force to the dorsal side of the calf. The compressive force is preferably a progressive force which starts toward the lower portion of the calf and progresses upward to the upper portion of the calf. The calf compression portion and the foot compression portion may be connected together to facilitate proper placement of the foot compression portion and calf compression portion.
The attachment between the foot compression portion and calf compression portion may also be severable in order to allow use of the calf compression portion apart from the foot compression portion. Such a feature allows a physician to apply calf compression therapy in order to increase the vascular blood flow. By applying calf compression therapy without foot compression therapy, blood flow can be increased in patient groups with extremely sensitive feet. After calf compression therapy has been applied, it may later be desirable to add foot compression therapy. This may be accomplished by simply placing the detached foot compression portion onto the patient for use in conjunction with the calf compression portion.
The compressive forces of both the foot compression portion and calf compression portion are preferably generated by an inflatable bladder enclosed within a retaining structure. The preferred retaining structure is pile material (such as that used by hook and pile fasteners) that encloses the inflatable bladders. Double-sided hook devices may then be used to retain straps at the locations which hold the bladder of the foot compression portion or the bladder of the calf compression portion in place.
The inflatable bladders of the foot compression portion and calf compression portion are preferably separate so that each can be inflated independently. The bladders are preferably filled by a large bore fitting adapter to carry fluid from a fluid source to the appropriate bladder.
The inflation, deflation, and delay rate as well as the pressure are adjustable over a wide range of parameters. Thus, when both the foot and calf inflation portions are used together, they may be inflated either simultaneously or progressively.
It is therefore a primary object of the present invention to provide for a medical device that increases vascular blood flow in the lower extremities that can be used with a wide range of patients, including those in sensitive patient classes.
Another object of the present invention is to provide for a medical device that improves vascular blood flow in the lower extremities and that allows visual inspection and monitoring of the midtarsal region of the foot.
Another object of the present invention is to provide for a medical device that improves vascular blood flow in the lower extremities and that allows visual and/or instrumental monitoring of blood flow in the midtarsal region of the foot.
Yet another object of the present invention is to provide for a medical device that improves vascular blood flow in the lower extremities that provides compression therapy to the foot and calf, or to the calf alone.
A still further object of the present invention is to provide a medical device that improves vascular blood flow in the lower extremities and that also reduces or eliminates tissue breakdown in the midtarsal region.
Another object of the present invention is to provide a medical device that can be used to treat deep vein thrombosis both by creating high blood velocities and by moving large blood volumes through rapid compression of areas of the foot, ankle, and calf.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the present invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by practice of the invention as set forth hereinafter.